Transcript Chapter 19-1 - Prokaryotes New Technology Leads to New Discovery   The invention of the microscope allowed humans to see things never before seen The work of Hooke and.

Chapter 19-1 - Prokaryotes
New Technology Leads to New
Discovery
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The invention of
the microscope
allowed humans to
see things never
before seen
The work of
Hooke and van
Leeuwenhoek
opened our eyes
to the world of
microorganisms
Prokaryotes
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Prokaryote – a single-celled organism
that lacks a nucleus (“pro” = before,
“karyote” = nucleus)
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Prokaryotes are typically referred to as
bacteria
Prokaryotes are the smallest & most common
microorganisms
Prokaryotes cover nearly ever centimeter of
the earth
Prokaryotes are the oldest and most
successful organisms on the planet
Prokaryotic Cell Structure
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A typical prokaryotic cell has a cell wall, cell
membrane, cytoplasm, DNA, ribosomes, flagella,
and pili
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Flagella (pl. flagellum) – a whip-like structure used
for movement
Pili – projections on the outer part of the cell
involved in cell to cell contact
DNA – bacteria have a single, circular chromosome
and small circles of DNA called plasmids
Capsule – an outer covering that helps protect the
bacteria cell
Bacteria have no membrane-bound organelles
(nucleus, mitochondria, etc.)
Classifying Prokaryotes
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There are 2 kingdoms of bacteria:
1. Eubacteria
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“true bacteria”
Well adapted to most current earth habitats\
The bacteria we refer to as “germs” are
eubacteria
2. Archaebacteria
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“ancient bacteria”
Well adapted to extreme habitats, some of which
may closely resemble the ancient earth (~3bya)
Eubacteria: A closer look
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Most prokaryotes are eubacteria
The kingdom eubacteria includes a wide
range of bacteria with varying habitats
and lifestyles
The cell walls of eubacteria are composed
of a carbohydrate called peptidoglycan
Eubacteria are found all around, on, and
in us, all the time, wherever we go!
Archaebacteria: A closer look
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Archaebacteria are similar in structure to
eubacteria, yet have a few key
differences:
No peptidoglycan in cell wall
Different membrane lipids
Live in extreme environments (high salt,
high heat, etc.)
An ancestor to
eukaryotes?
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Certain important
archaebacteria genes
(EX. RNA polymerase
gene) are more
similar to eukaryotic
genes than to
eubacterial genes
Scientists now believe
this is evidence that
eukaryotes evolved
from archaebacteria,
and are not directly
descended from the
more common
eubacteria
Types of Archaebacteria
1. Methanogens – Live in environments with no
oxygen (mud pits, landfills, intestinal tracts)
and get energy by converting H2 and CO2 into
CH4 (methane)
2. Extreme Halophiles – Live in high salt
environments, use salt to generate ATP
3. Thermoacidophiles – Live in acidic and/or
high temperature environments (hydrothermal
vents, volcanoes, hot springs) and get energy
by breaking down sulfur compounds
Identifying Prokaryotes
Shapes – Prokaryotes usually have one of
three shapes:
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1. Bacilli (bacillus) – rod-shaped bacteria
2. Cocci (coccus) – spherical bacteria
3. Spirilla (spirillum) – spiral-shaped bacteria
Some bacteria-naming prefixes:
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Diplo = pairs of cells (EX. Diplobacilli)
Staphylo = clusters of cells (EX. Staphylococcus)
Strepto = chains of cells (EX. Streptococcus)
Identifying Prokaryotes
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Cell Walls – Eubacteria have 2 different types
of cells walls (single or double)
Gram staining is a process used to indicate the
cell wall type – two stains, violet and pink, are
applied and the bacteria are then observed
1. Gram-positive bacteria have a a cell wall made
of a thick peptidoglycan layer (single wall) and
appear purple when stained (both stains absorbed)
2. Gram-negative bacteria have a cell wall made of
a thin peptidoglycan layer and an outer lipid layer
(double wall), and appear pink when Gram stained
(only pink stain is absorbed)
Obtaining Energy
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Some bacteria are autotrophs (“selffeeders”) that make their own organic
molecules (food)
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Photoautotrophs – bacteria that carry out
photosynthesis similar to plants
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EX. Cyanobacteria contain light absorbing
pigments and are found all over the world
Chemoautotrophs – bacteria that make
organic molecules using energy from the
breakdown of inorganic (no carbon) molecules
such as ammonia or sulfur
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EX. Bacteria living on or around hydrothermal
vents on the ocean floor
Obtaining Energy
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Some bacteria are heterotrophs (“otherfeeders”) that get energy by taking in
organic molecules (eating).
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Heterotrophic bacteria compete with humans
for food (food “spoilage” is due to bacteria)
Many heterotrophic bacteria secrete toxic
chemicals to prevent other organisms from
stealing their food
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EX. Salmonella bacteria secrete a toxic substance
that causes food poisoning
Obtaining Energy
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Some bacteria are photoheterotrophs
that capture sunlight for energy and
consume organic molecules
Carrying Out Respiration
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Bacteria get energy by breaking down
molecules during the process of
respiration and/or fermentation
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Obligate aerobes (aerobic bacteria) require
oxygen and depend mainly on respiration for
energy
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The necessary proteins for respiration are found in
the cell membrane (bacteria have no
mitochondria)
Carrying Out Respiration
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Obligate anaerobes (anaerobic bacteria) do
not require oxygen and cannot survive in
oxygen-rich environments
Fermentation only
 EX. Clostridium tetani, Clostridium botulinum
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Facultative anaerobes can survive with or
without oxygen
Able to switch between respiration and
fermentation
 Can survive just about anywhere
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Growth and Reproduction
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In favorable conditions, prokaryotes can
grow and divide quickly
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A single prokaryotic organism with unlimited
resources, dividing every 20 minutes, would
produce a mass of bacteria 4000X the mass of
the earth in 48 hours
This doesn’t happen due to lack of resources
and the production of waste
Growth and
Reproduction
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Bacteria reproduce by
binary fission
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Cell grows until double
in size
DNA is replicated
Cell splits in half
producing identical
daughter cells
Binary fission is
asexual
reproduction, it does
not involve the
exchange or
recombination of
genetic information (all
DNA comes from one
parent)
Growth and Reproduction
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Conjugation – process where a DNA plasmid is
copied and passed from one bacteria cell to
another
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Two bacteria are joined by pilus
DNA plasmids move from one cell to the other
This increases the genetic diversity of a bacteria
population
Transformation – when bacteria take up
pieces of DNA secreted by live bacteria or
released by dead bacteria giving them new traits
Growth and Reproduction
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Some bacteria are able to survive harsh
environmental conditions for long periods
Endospore – A thick, internal wall enclosing a
bacteria cell’s DNA and a portion of the
cytoplasm
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Formed when growth conditions are unfavorable
Can remain dormant for months or even hundreds of
years
Makes it possible for bacteria to survive harsh
conditions (extreme heat, lack of food, etc.)
Chapter 19-2 – Bacteria in Nature
Bacteria play an essential role in
maintaining the ecosystem
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Decomposer – organism that breaks down
dead organisms/organic material for food
Many bacteria are decomposers
Decomposers break down dead matter into
simpler substances which are released to the soil
where they can be reused by plants
What would happen without decomposers?
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There would be dead stuff piled up everywhere!
Bacteria play an essential role in
maintaining the ecosystem
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Nitrogen Fixation – The process of converting
atmospheric nitrogen gas (N2) to ammonia
(NH3) or other nitrogen compounds that plants
can use
Plants need nitrogen to make amino acids which
in turn are used to make proteins
Plants cannot use N2 directly
Nitrogen-fixing bacteria provide enrich the soil
with nitrogen containing compounds
Animals get their nitrogen from plants (either
directly or indirectly)
Bacteria and Disease
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There are approximately 10X as many bacteria
cells in you than human cells
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Most are on your skin or somewhere in your digestive
system
These bacteria are kept under control by your
immune system
A few are actually beneficial
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Aid in digestion
Produce necessary vitamins
Compete for living space with potentially harmful bacteria
Escherichia coli in the
human intestines
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E. coli normally colonizes
an infant's intestines
within 40 hours of birth,
arriving with food or
water or with the
individuals handling the
child
Harmless strains of E. coli
benefit the host by
producing vitamin K
(necessary for blood
coagulation)
They also prevent
harmful bacteria from
becoming established in
the intestine
Bacteria and Disease
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A few types of bacteria cause disease
(pathogenic bacteria)
Pathogen – a disease-causing agent, like
some bacteria
Bacteria cause disease in one of two general
ways:
1. Damaging tissues of host organism by breaking
them down for food
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EX. Tuberculosis bacteria break down lung tissue
2. Releasing toxins that harm the body
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EX. Tetanus is caused by a neurotoxin produced by
Clostridium tetani bacteria
Bacterial
Diseases
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Tetanus
Typhoid Fever
Diptheria
Syphilis
Cholera
Food poisoning
Leprosy
Tuberculosis
Meningitis
Bacteria and Disease
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Many bacterial diseases can be prevented
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Vaccines stimulate the body’s immune system and
prevent bacteria from colonizing body tissues
Antibiotics – compounds that block the growth or
reproduction of bacteria
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Penicillin, the first antibiotic, was developed in 1942
For the first time, humans had a way to treat bacterial
infections (short of sawing off appendages!)
Good personal/environmental hygiene help prevent
bacterial infections from spreading (hand washing,
sewage system, etc.)
Major reason for increased life expectancy =
increased knowledge of preventing and treating
bacterial diseases
The discovery
of antibiotics
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1928 -Alexander Fleming
investigates staphylococci.
August 1928 - Fleming goes
on vacation, leaves all his
cultures of staphylococci on a
bench in the lab
On returning, Fleming notices
that one that the colonies of
staphylococci culture was
contaminated with a fungus,
and bacteria that had
immediately surrounded it
had been destroyed
The fungus was from a group
of fungi called Penicillum, and
he called the bacteria-killing
substance it produced
penicillin
Discovery of Penicillin
Antibiotic Resistance – Too much of
a good thing?
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Many bacteria have developed resistance to
certain antibiotics
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The more we use antibiotics, the more we risk the
development of resistant bacteria strains
Antibiotics are frequently prescribed unnecessarily,
and taken irresponsibly
Antibiotics are used extensively in agriculture
In some cases, bacteria can be resistant to more
than one type of antibiotic
Resistance is determined by genes, and can be
transferred from one bacteria to another via
transformation or transduction
Antibiotic resistance poses a significant problem
for human health now and in the future
Controlling Bacteria
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Sterilization – destroying bacteria with either
heat or chemicals
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Refrigeration/freezing prevents food spoilage
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Cooking food kills most bacteria
Disinfectant – a chemical solution that kills bacteria
Bacteria grow more slowly at low temperatures
Different preservation techniques can be used to
store food for long periods
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Canning – sealing sterilized food in cans or glass jars
Salting – draws moisture out of food/bacteria cells
Pickling – vinegar is highly acidic and prevents most
bacterial growth
Canning Tomatoes
250 lbs of tomatoes + 10-12 hours = 45 to 50
quarts of crushed tomatoes
Human Uses of Bacteria
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Bacteria are used in the production of a
variety of foods
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Cheeses, buttermilk, yogurt, sour cream,
pickles, sauerkraut, vinegar
Bacteria are used in industry
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Water treatment, oil spill clean up, botox
Insulin is produced using bioengineered
bacteria, as is human growth hormone,
antibiotics, and other chemicals